Heat exchange apparatus

ABSTRACT

A heat exchange apparatus for use in the production of sugar confectionery or for tempering chocolate including a vessel with a tubular heat transfer surface. The vessel defines an inlet and outlet higher than the inlet. Heat exchangers, such as steam jackets and modulating valves are provided for supplying heat to or removing heat from the heat transfer surface. A shaft is located longitudinally along the length of the vessel and is provided with at least one piston. The shaft is reciprocated in the vessel so that the product is agitated and substantially the entire heat transfer surface of the vessel is swept by the piston during each reciprocation cycle.

TECHNICAL FIELD

The present invention relates to a heat exchange apparatus which isprimarily for use in the manufacture of sugar confectionery andchocolate products. In particular, the invention relates to heatexchanging apparatus which can be adapted to operate either asevaporation apparatus for use in the manufacture of toffee and sugarconfectionery or as tempering apparatus for use in the manufacture ofchocolate confectionery.

BACKGROUND OF THE INVENTION

In order to manufacture high quality toffee, it is necessary toevaporate water from the ingredient mix continually during the cookingprocess in order to obtain a fine flavour and consistency in thefinished product. In addition, as the ingredients contain a highproportion of sticky milk proteins, which are highly susceptible toburning, it is necessary to agitate the mix continually during cookingin order to prevent it from sticking to the heat transfer surfaces ofthe vessel and burning. Such agitation is also necessary to produce afine mix of the ingredients.

While traditionally toffee was manufactured by boiling the toffeeingredients in batches in open vessels, such a method does not lenditself to mass production. Various apparatus are known for themanufacture of toffee by a continuous process.

For example, in EP-A-0 061 232 is disclosed an evaporation apparatus foruse in the cooking of toffee wherein a heated closed vessel iscontinuously fed with an ingredient mix via the base of the vessel andthe cooked mix is permitted to overflow over a weir out of the top ofthe vessel. Rotating paddles within the vessel swirl the ingredient mixinto a vortex in order to prevent it sticking to the interior of thevessel. The extremities of the vortex are also urged towards the weir toexit the vessel.

In contrast, in the use of chocolate in the production of confectioneryitems, it is necessary to temper the molten chocolate mix in order toprevent fat bloom from occurring in the finished product and to give agood appearance to the finished item. Fat bloom is likely to occur whenchocolate has been poorly mixed and solidified during production.Tempering of the chocolate is, therefore, carried out to mix theingredients thoroughly and to control the crystallization of the variousfats within the mix. Such tempering is generally achieved by heating thechocolate to melt all fat crystals therein and thereafter controllingits cooling, whilst at the same time stirring or agitating it, so thatstable fat crystals are only slowly formed therein.

It is, however, again convenient if chocolate tempering can be carriedout as a continuous process within a confectionery manufacturing processas a whole.

SUMMARY OF THE INVENTION

The present invention is intended to provide a heat exchange apparatuswhich can be used either as an evaporation apparatus or cooker for usein the manufacture of sugar confectionery, such as toffee, or as atempering apparatus for use in the production of chocolateconfectionery.

According to a first aspect of the present invention there is provided aheat exchange apparatus, for example for use in the production of aconfectionery or chocolate product, comprising a vessel with a tubularheat transfer surface and defining an inlet and an outlet, heat exchangemeans for supplying heat to or removing heat from the heat transfersurface, and characterized in that a shaft is located longitudinallyalong the length of the vessel and is provided with at least one piston,and means are provided for reciprocating said shaft within the vesselwhereby substantially said entire heat transfer surface of the vessel isswept by the piston during at least each reciprocation cycle.

Preferably, the heat transfer surface comprises a substantiallycylindrical surface.

Preferably also, a plurality of spaced pistons are provided along thelength of the shaft whereby on reciprocation of the shaft substantiallythe entire heat transfer surface of the vessel is swept by the pistonsduring each reciprocation cycle.

Preferably also, each piston comprises a disc defining at least one holetherethrough.

Advantageously, the vessel comprises a substantially vertical columnwith the outlet located at a higher level than the inlet.

Preferably also, the heat exchange means are supplied with a heattransfer fluid via a modulating valve.

Preferably also, at least one sensor is provided from which thetemperature within the vessel can be deduced and means are provided forcontrolling operation of the modulating valve to increase or to restrictthe rate at which the heat transfer fluid is supplied to the heatexchange means dependent on said temperature. A plurality of sensors mayalso be provided along the length of the vessel and the heat exchangemeans adapted to enable a temperature gradient to be set up along thelength of the vessel.

According to a second aspect of the present invention there is providedan evaporation apparatus for use in the manufacture of sugarconfectionery comprising a vessel with a tubular heat transfer surfaceand defining an inlet and an outlet higher than the inlet, and heatsupply means for supplying heat to the heat transfer surface, andcharacterised in that a shaft is located longitudinally along the lengthof the vessel and is provided with a plurality of spaced pistons, and inthat means are provided for reciprocating said shaft within the vesselwhereby substantially said entire heat transfer surface of the vessel isswept by the pistons during at least each reciprocation cycle.

According to a third aspect of the present invention there is provided achocolate tempering apparatus comprising a vessel with a tubular heattransfer surface and defining an inlet and an outlet higher than theinlet, and heat exchange means for transferring heat to or from the heattransfer surface, and characterised in that a shaft is locatedlongitudinally along the length of the vessel and is provided with aplurality of spaced pistons, and means are provided for reciprocatingsaid shaft within the vessel whereby substantially said entire heattransfer surface of the vessel is swept by the pistons during at leasteach reciprocation cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example withreference to the accompanying drawings in which:

FIG. 1 is a schematic cross-section of a heat exchange apparatusaccording to the present invention which is adapted for use as aconfectionery cooker:

FIG. 2 is a section along the line II--II of FIG. 1 showing, to anenlarged scale one of a plurality of pistons forming part of theinvention; and

FIG. 3 is a part section along the line indicated in FIG. 2, again to anenlarged scale.

DETAILED DESCRIPTION OF THE INVENTION

The confectionery cooker shown in FIG. 1 comprises a columnar vessel 1defining a interior heat transfer surface 2 which is preferablysubstantially cylindrical, as shown. The vessel 1 is preferably made upof several sections 3, 4, two being the number shown in FIG. 1 but moresections could be used if appropriate. Each of these sections 3, 4comprises a heating jacket 5 surrounded by heat insulation 6. Eachjacket 5 is independently supplied with steam or other heat transferfluid at a typical pressure of around 10 bar via a modulating valve 7.The steam or other heat transfer fluid exits from each jacket 5 via asuitable strainer 8 and, in the case of steam, a condensate trap 9 fromwhich it or its condensate can be recycled.

The vessel 1 is closed at its base but comprises an inlet 10 at its baseto which is connected a premixed supply of ingredients via a reversiblemetering pump 11 and pipework 12. As is conventional, the ingredientsfor the confectionery product being manufactured are supplied to thevessel 1 in a premixed form from a holding tank (not shown). The rate ofsupply is controlled by the operating speed of the metering pump 11,which can be adjusted to regulate the residence time of the product mixwithin the vessel and therefore the rate at which the product isproduced. The pump 11 can also be reversed and operated in an oppositesense if required. Although not part of the evaporation process, it isuseful to have this facility to enable the vessel 1 to be drained, forexample for maintenance and cleaning purposes.

The top of the vessel 1 is not closed and defines an outlet 13 which iscovered by an outlet arrangement 14. The arrangement 14 is hinged to thevessel 1 and, when closed, is sealed against the vessel 1 around theoutlet 13. The arrangement thereby comprises a lid which is shaped so asto flare outwardly in an upward direction to increase the surface areaof the product mix exiting from the vessel 1 and thereby aid furthermoisture evaporation therefrom prior to output from the cooker. At oneside of the cover 14 is provided a product outlet tube 15 which extendssubstantially horizontally and then downwardly away from the cooker.Within this tube 15, at the joint between the horizontally anddownwardly extending sections is located a weir 16 of adjustable heightwith respect to the tube 15. In order to exit the cooker, therefore, theproduct mix must rise sufficiently within the cooker to cascade over theweir 16, the height of which, in conjunction with the operating speed ofthe metering pump 11, can be used to control the retention time of theproduct mix within the vessel 1. In general, the height of the weirprovides a means of fine adjustment of this retention time.

The upper part of the arrangement 14 also comprises a moisture outlettube 17 leading to an extraction duct 18 so that moisture and volatilematter are drawn away from the interior of the vessel 1 to enhancefurther evaporation from the product mix.

For the production of some forms of confectionery it is alsoadvantageous to reduce the pressure within the vessel 1 to cause boilingof the product therein at a lower temperature. It will be appreciatedthat in these cases, it is possible to modify the outlet arrangement 14to include a means for the vacuum extraction of the vapor therein toreduce the pressure within the vessel 1.

At the vessel outlet 13, just inside the cover arrangement 14, islocated a temperature probe 19 which is linked to the modulating valve 7via a transducer 20. The temperature of the product exiting from thevessel 1 is an indication of its moisture content and thereby of thedegree to which it has been cooked. The signal from the temperaturesensor 19 can thus be used to cause operation of the valve 7 to increaseor to restrict the rate at which steam or other heat transfer fluid issupplied to the jackets 5 and thereby increase or decrease thetemperature of the product mix in order to ensure that sufficientevaporation from the product has occurred. It will be appreciated thatthe temperature sensor 19 could be replaced by a moisture meter.Likewise, the position of the sensor could be varied, for example itcould be located within the product outlet tube 15.

In a modification, a plurality of temperature or moisture sensors 19 canbe used, to measure the temperature or moisture level of the product atthe different levels within each section 3, 4 of the vessel. In thisway, by increasing the number of sections 3, 4 and/or the number ofjackets 5 for the vessel 1 as a whole, and by also providing individualmodulating valves 7 each linked to a temperature or moisture sensor 18for each jacket 6, a temperature gradient can be set up within thevessel with the product mix being gradually heated to higher and highertemperatures as it rises within the vessel 1.

In order to prevent the product mix in contact with the heated interiorsurface 2 of the vessel 1 from being burnt, it is necessary to agitateconstantly the product mix within the vessel 1. To this end, an agitator21 is located within the vessel 1.

The agitator 21 comprises a reciprocable shaft 22 which is locatedaxially within the vessel 1 and runs from its base to its outlet 13.Attached to the shaft 22 at regular intervals along its length is aplurality of pistons 23. The shaft 22 can be reciprocated within thecylindrical column of the vessel 1 by any convenient means, such as, acrank shaft and piston rod arrangement, or a hydraulic or pneumaticpiston located beneath the vessel 1 or, as shown in FIG. 1, by a rotarycam arrangement 24 which in combination with spring means 25 operate toa drive the shaft upwards and downwards in the vessel 1. The degree ofreciprocation required is directly dependent on the axial spacing of thepistons 23 along the shaft 22. It is important that in use of the vessel1, the agitator 21 operates so that substantially the entire heattransfer surface 2 of the vessel 1 is swept by the pistons 23 during atleast each reciprocation cycle or preferably each half-cycle, as in thepresent example. In this way none of the product mix can remain incontact with the surface 2 for any length of time sufficient to causeburning of same. Thus, the number and spacing of the pistons 23 isdependent on the distance that is travelled by the shaft during eachreciprocation cycle. To some extent, this will be determined by theviscosity of the product mix; the more viscous the product mix, theshorter the travel of the shaft 22 and the greater the number of pistons23 required. In addition, the rate at which heat is transferred to theproduct mix is also a function of the speed of reciprocation of thepistons 23 and the rate of reciprocation can be determined accordinglyaccording to the nature of the product mix.

As shown in FIGS. 2 and 3, each of the pistons 23 comprises a disc 26with a central hub 27 that is either welded to or clamped to the shaft22, for example in the latter case via clamping screws 28. The pistons23 are, therefore, readily replaceable when required. The disc 26 ofeach piston 23 also defines a plurality of circular holes 29, typicallysix, which are regularly arranged, around the hub 27. These permit theshaft 22 to be reciprocated through the product mix and the product mixto rise up the vessel 1. In addition, as the product mix passes throughthe holes 29 it is swirled and agitated so that it becomes thoroughlymixed. Agitation and turbulence within the product mix can also beincreased by attaching angled flat bar spacers or fins (not shown) tothe surface of the disc 26 and by at least partially rotating the shaft22 about its longitudinal axis.

Around the rim of each piston 23 is located at least one and preferablytwo piston rings 30 which act as scrapers. The rings 30 are located inperipheral grooves 31 formed in the rim and form a seal against thecylindrical interior heat transfer surface 2 of the vessel 1. Each ring30 is not quite annular so that a small gap 32 is left between the endsof the ring 30 but the gaps in each of the two rings 30 of each piston23 are deliberately not aligned. In this way, no area of the surface 2is left unswept by the rings 30 during reciprocation of the shaft 22 toensure that none of the product mix can burn on to the surface 2.

Preferably, while the pistons 23 are made either of stainless steel or afood grade hard plastics material such as polytetrafluoroethylene(PTFE), the rings 30 are usually be formed from a resilient food gradeplastics material to enhance their scraping effect.

In a further modification, the cooker can be adapted to aerate theproduct mix during cooking and/or to create an aerated product. In thiscase, pressurized air is introduced into the base of the vessel throughan inlet pipe 33 at a predetermined rate dependent on the rate ofoperation of the pump 11. Bubbles of air are then thoroughlyincorporated into the product mix by the agitator 21 during cooking.

Turning now to use of the heat exchange apparatus according to theinvention as a chocolate tempering apparatus, it will be appreciatedthat here the vessel 1 is not used for cooking the chocolate mix thereinbut to control its cooling. The apparatus is, therefore, operated in adifferent fashion while in construction remaining essentially the same.As, however, evaporation is not required from a chocolate mix, themoisture outlet tube 17 and extraction duct 18 are not required. It willalso be appreciated in this regard that in this case the sensors 19 mustcomprise temperature sensors rather than moisture sensors and that theheat transfer fluid used cannot be steam, which is too hot forchocolate, but is typically water.

With reference to FIG. 1 and as previously referred to, the apparatus ismodified by increasing the number of sections 3, 4 and/or the number ofjackets 5 for the vessel 1 as a whole, and also by providing individualmodulating valves 7 and temperature sensors 19 for each jacket 5. Bycontinuously monitoring the temperature of the chocolate mix as ittravels up the vessel 1 and by controlling the temperature of the heattransfer fluid within the jackets 5, a temperature gradient can be setup within the vessel 1.

It is expected that the lowermost section 3 of the vessel 1, will beused to heat the chocolate mix to ensure that it is fully fluid with allfat crystals melted, although alternatively the chocolate mix could besupplied to the vessel in a pre-heated condition. Then, as the chocolatemix rises in the vessel 1 it is progressively cooled by the jackets 5 inorder that crystallization of the various fats within the chocolate mixis carefully controlled to ensure a stable end product. At the sametime, the vigorous agitation of the chocolate mix by the agitator 21ensures that individual crystals do not grow too large and that thechocolate mix is well blended. The scraping action of the pistons 23also ensures that the mix does not stick to the surfaces 2 nor largercrystals form there. Thus a consistent chocolate can be produced with agood temper.

As in the confectionery cooker, when used for chocolate tempering thechocolate mix is intended to overflow from the vessel 1 into the outletpipe 15 over the weir 16. The height of the weir 16, in conjunction withthe operating speed of the metering pump 11, can therefore be used tocontrol the retention time of the chocolate mix within the vessel 1,with the height of the weir providing a means of fine adjustment.

The apparatus can also be used to produce an aerated chocolate productin a similar manner to the confectionery cooker. The air inlet pipe 33can be used to introduce pressurized air into the base of the vessel 1at a predetermined rate dependent on the rate of operation of the pump11. Fine bubbles of air are then thoroughly incorporated into thechocolate mix by the agitator 20 during its cooling.

In both examples described above, the heat exchange apparatus of theinvention has advantages over conventional confectionery cookers andchocolate tempering apparatus. The apparatus is compact and ofrelatively simple construction. The sectional form of the vessel 1permits it to be both constructed and taken apart for maintenancequickly and easily. In addition, as the agitator 21 is driven frombeneath the vessel 1, any danger of contamination of the product withinthe vessel 1 from, for example, the leakage of oil or other contaminantsfrom the its drive means is avoided. Likewise, the cost of providingshielding means for preventing such contamination is also avoided.

It is anticipated that the vessel 1 will be made, for example, of mildor stainless steel and each section 3, 4 will have an overall length ofaround 1250 mm and an internal diameter of around 350 mm. However, thesedimensions can be varied to suit the particular application of theapparatus. Advantageously, the vessel 1 will be mounted on a standwhereby, when not in use, it can be uncoupled from the various supplyand outlet pipes and swivelled from a vertical into a horizontalposition. In this way, the agitator 21 can be easily withdrawn from thevessel 1 for maintenance and repair. In addition, it will be possible tomodify the form of the agitator 21 to suit various different types ofproduct. For example, the number of the pistons 23 may be altered, asmay the size, shape and number of holes 29 therein. More fundamentally,the agitator itself could be altered to suit the production of differenttypes of confectionery products. For example, it is necessary to cooksome types of confectionery quickly. In these circumstances, thediameter of the shaft 22 can be increased which will have the effect ofincreasing the relative quantity of the product mix in contact with theheat transfer surfaces 2. All other things remaining equal, therefore,such a product mix will be cooked faster than would otherwise be thecase. In some circumstances, it may also be appropriate to modify theagitator 21 by the use of a hollow shaft 22 through which the heattransfer fluid can also be circulated by a suitable means at anappropriate temperature sufficient to increase heat transfer to or fromthe product mix but not sufficient to cause burning or excessive coolingof the product mix in contact therewith.

The apparatus could also be modified to operate solely as an aerator forcertain products. In these circumstances, the heating jacket 5 and heatinsulation 6 can be dispensed with and the agitator 21 simply used tomix the product generally and to mix in bubbles of pressurized airsupplied by the air inlet pipe 33. The foregoing disclosure anddescription of the invention is illustrative and explanatory thereof.Various changes in the details of the illustrated construction may bemade within the scope of the appended claims without departing from thetrue spirit of the invention. The present invention should only belimited by the following claims and their legal equivalents.

I claim:
 1. A heat apparatus for use in the production of aconfectionery or chocolate product comprising a vessel with a tubularheat transfer surface, said vessel defining an inlet and an outlet, heatexchange means for supplying heat to or removing heat from the heattransfer surface, a shaft located longitudinally along a length of thevessel and provided with at least one piston, and means forreciprocating said shaft within the vessel whereby substantiallyentirely said heat transfer surface of the vessel is swept by the pistonduring at least each reciprocation cycle, and wherein the heat exchangemeans are supplied with a heat transfer fluid from a modulating valve,and in that, at least one sensor is interactive with said vessel so asto deduce a temperature within the vessel, and control means areprovided for controlling operation of the modulating valve to increaseor to restrict a rate at which the heat transfer fluid is supplied tothe heat exchange means dependent on said temperature.
 2. The apparatusas claimed in claim 1, wherein the heat transfer surface comprises asubstantially cylindrical surface.
 3. The apparatus as claimed in claim1, wherein a plurality of spaced pistons are provided along a length ofthe shaft whereby on reciprocation of the shaft substantially entirelysaid heat transfer surface of the vessel is swept by the pistons duringat least each reciprocation cycle.
 4. The apparatus as claimed in claim3, wherein said heat transfer surface of the vessel is swept by thepistons during each reciprocation half-cycle.
 5. The apparatus asclaimed in claim 1 wherein each piston comprises a disc defining atleast one hole extending therethrough.
 6. The apparatus as claimed inclaim 1 wherein each piston has at least one piston ring around a rim ofsaid piston.
 7. The apparatus as claimed in claim 6, wherein at leasttwo piston rings are provided on each piston, said piston rings havinggaps formed between ends of said piston rings around a periphery of saidpiston, said gaps being offset from one another.
 8. The apparatus asclaimed in claim 1 wherein the vessel comprises a substantially verticalcolumn with the outlet located at a higher level than the inlet.
 9. Theapparatus as claimed in claims 1 wherein the shaft is hollow and meansare provided for circulating said heat transfer fluid therethrough. 10.The apparatus as claimed in claim 1 wherein a plurality of sensors areprovided along the length of the vessel and the heat exchange means areadapted to enable a temperature gradient to be set up along the lengthof the vessel.
 11. The apparatus as claimed in claim 1, wherein eachsensor comprises a temperature sensor.
 12. The apparatus as claimed inclaim 1, wherein each sensor comprises a moisture sensor.
 13. Theapparatus as claimed in claim 1 wherein means are provided for supplyingpressurized air to an interior of the vessel for aeration of the productduring production.
 14. An evaporation apparatus for use in themanufacture of sugar confectionery comprising a vessel with a tubularheat transfer surface and defining an inlet and an outlet positionedhigher than the inlet, and heat supply means for supplying heat to theheat transfer surface, a shaft located longitudinally along a length ofthe vessel and provided with a plurality of spaced pistons, and meansfor reciprocating said shaft within the vessel whereby substantiallyentirely said heat transfer surface of the vessel is swept by thepistons during at least each reciprocation cycle, and wherein the heatsupply means are supplied with a heat transfer fluid from a modulatingvalve, and in that at least one sensor is provided for deducing atemperature within the vessel, and control means are provided forcontrolling operation of the modulating valve to increase or to restricta rate at which the heat transfer fluid is supplied to the heat supplymeans dependent on said temperature.
 15. A chocolate tempering apparatuscomprising a vessel with a tubular heat transfer surface and defining aninlet and an outlet positioned higher than the inlet, and heat exchangemeans for transferring heat to or from the heat transfer surface, ashaft located longitudinally along a length of the vessel and providedwith a plurality of spaced pistons, and means for reciprocating saidshaft within the vessel whereby substantially entirely said heattransfer surface of the vessel is swept by the pistons during at leasteach reciprocation cycle, and wherein the heat exchange means aresupplied with a heat transfer fluid from a modulating valve, and in thatat least one sensor is is adapted to deduce a temperature within thevessel and control means are provided for controlling operation of themodulating valve to increase or to restrict the rate at which the heattransfer fluid is supplied to the heat exchange means dependent on saidtemperature.